Low profile keyboard switch

ABSTRACT

A pushbutton switch has a base and a button telescopically movable on the base. There are a pair of terminals with one of the terminals having a contact arm positioned within a switching chamber in the base. Movement of the button is effective to cause the contact arm to close upon the other terminal. The effective length of the contact arm is greater than its actual length and is greater than the length of any side of the base.

'United States Patent 191 I Golbeck et al.

[ Oct. 28,1975

LOW PROFILE KEYBOARD SWITCH Inventors: Bernard J. Golbeck, Crystal Lake; Raymond F. Lewandowski, Mount Prospect; William C. Markison, Crystal Lake, all of Ill.

Assignee: Oak Industries, Inc., Crystal Lake,

Filed: Apr. 29, 1974 Appl. No.: 465,112

Related U.S. Application Data Continuation-in-part of Ser'. No. 279,378, Aug. 10, 1972, abandoned.

References Cited UNITED STATES PATENTS 3/1919 Manson 200/159 A 7/1924 JamesM; 200/159 A 2,499,958 3 /1950 Kn owlton ZOO/159A III III i-Tii 2,584,460 2/1952 Jacobs, Jr. 200/67 DA 3,131,265 4/1964 Toruk 1 200/6 BB 3,139,500 6/1964 Fallon et al. 1 200/67 DA 3,185,803 5/1965 Driscoll 200/159 A 3,274,355 9/1966 Francy 200/77 3,663,780 5/1972 Golbeck 200/159 R X 3,749,872 7/1973 Foster 200/158 A X FOREIGN PATENTS OR APPLICATIONS 506,462 11/1951 Belgium ZOO/I59 A Primary Examiner-James R. Scott Attorney, Agent, or Firml(inzer, Plyer, Dorn & McEachran 57 ABSTRACT 13 Claims, 13 Drawing Figures U.S. Patent Oct. 28, 1975 Sheet 1 of2 3,916,131

U.S. Patent Oct. 28, 1975 Sheet 2 of2 3,916,131

LOW PROFILE KEYBOARD SWITCH SUMMARY OF THE INVENTION This application is a continuation-in-part of our copending application Ser. No. 279,378, filed Aug. 10, 1972, now abandoned.

The present invention relates to pushbutton switches and in particular to a pushbutton switch having a long life cycle.

A primary purpose of the invention is a pushbotton switch in which the contact arm has an effective length greater than its actual length.

Another purpose is a pushbutton switch in which the contact arm is diagonally positioned within the switching chamber.

Another purpose is a pushbutton switch having a contact arm of extended length to provide a longer life cycle for the switch.

Another purpose is a pushbutton switch of the type described having guide means to maintain alignment between the button and base.

Another purpose is a reliably operable simply constructed pushbutton switch of the type described.

Another purpose is a pushbutton switch in which the guide means has portions thereof arranged to provide a snap-on connection between the button and base.

Another purpose is a pushbutton switch of the type described in which the button has an outwardly extending skirt, completely masking the base, to prevent spilled material from coming in contact with the electrical portions of the switch.

Other purposes will appear in the ensuing specification, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated diagrammatically in the following drawings wherein:

FIG. 1 is a plan view showing a portion of a keyboard with the pushbutton switch of the invention used thereon,

FIG. 2 is a section along plane 22 of FIG. 1,

FIG. 3 is a bottom view of the switch base, FIG. 4 is an enlarged top view of the switch base, FIG. 5 is an enlarged bottom view of the button, FIG. 6 is a partial section through the button and base illustrating a snapon connection,

FIG. 7 is a section along plane 77 of FIG. 4,

FIG. 8 is a partial vertical section showing a modified form of button,

FIG. 9 is a side view of a modified form of switch construction,

FIG. 10 is a top plan view of the base for the switch in FIG. 9,

FIG. 11 is an end view of the switch base of FIG. 10 with parts in section,

FIG. 12 is a bottom view of the button, for the switch in FIGS. 9, l0 and 11, and

FIG. 13 is a partial vertical section of a modified form of snap-on arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is useful as a keyboard switch, although it has wider application. An important consideration in such a switch is the contact arm, as it is one element which receives substantial wear and can cause the switch to become defective. In order to have a certain length of travel which permits positive opening and closing of the switch, and yet have a contact arm for the switch which will not break after lengthy use, it is desirable to increase the length of the contact arm. The longer the effective length of the contact arm, the less likelihood of the arm breaking after extensive use. Accordingly, the present invention is particularly directed to a pushbutton switch in which the effective length of the contact arm is greater than its actual length and is greater than the length of any side of the switch button.

In FIG. 1, a typical keyboard includes a plurality of switches 10, generally square in configuration, and a switch 12 which is approximately twice the size of the switch 10. The switches 10 and 12 may be conveniently mounted in a keyboard 14. As particularly shown in FIG. 2, the keyboard may include a printed circuit board 16 with the terminals 18 of each of the switches extending through and being soldered into the printed circuit board.

The switch 10 may include a base 20 and a button 22, each of which may be formed of a suitable plastic. The button is telescopically mounted on the base 20 for in and out movement. The base 20 may have four sides,

each of which is indicated at 24, and is generally square in cross section, although obviously the invention should not be limited to this configuration. There is a switching chamber 26 within the base 20 which is effectively formed by the four sides 24 and by the diagonal sides 50. The bottom 29 of the base has a plurality of feet 28 which are seated upon the printed circuit board when the switch is used in that application. Note particularly FIG. 2. Adjacent the feet 28 there is a peripherally extending ledge 30 which is formed and adapted to receive a stress relieving plate 32, again as illustrated in FIG. 2. The stress relieving plate 32 may be formed of steelor the like and will be spaced slightly away from i the printed circuit board. It will resist the applied force to the switch button so that the printed circuit board cannot be damaged by operation of the switch.

A pair of terminals 34 and 36 extend outwardly through openings 38 and 40 in the base 20. Terminal 34 has an inwardly bent portion 42 which extends inside of the switching chamber 26. Terminal 36 has a relatively thin substantially flat integral contact are 44, illustrated in detail in FIGS. 4 and 7. The contact arm 44 has a wedge-shaped portion 46 and a cut-out relatively thin substantially flat interior portion 48 which is bent upwardly toward the button 22. Note that the contact arm 44 extends diagonally from one comer of the base toward the opposite comer. The actual length of the contact arm 44 is greater than any one of the sides 24 of the base. Since the effective length of the contact arm is that portion which can be flexed when the button is operated, the effective length of the arm includes the length of the cutout portion 48, as well as the entire length of the contact arm itself. Thus, the effective length is substantially greater than the actual length.

The button 22 has the same number of sides and the same overall configuration as the base 20 and it is telescopically mounted on the base. Extending downwardly from the top of the button 22 is a switch operator 54 which is positioned to contact the cut-out portion 48 of the contact arm 44. Note particularly FIG. 7. Thus, as the button is depressed, the switch operator 54 will contact portion 48 of the contact arm to flex it, as well as the entire length of the contact arm, and

move the Contact arm toward contact portion 42 to complete a switching function. Coil spring 56 positioned between the button and the base will normally hold the button in the out position and thus the switch in the open position. However, the switch could be arranged for normally closed operation.

In order to properly align the switch element, there are guide means preferably formed along each of the mating sides of the button and base. Looking particularly at FIGS. 4 and 5, there may be a groove 58 formed along each of the sides 24 of the base. There are mating rails 60 formed along the interior of the button, with the rails riding in the grooves 58. Note that the width of the rails and grooves is small, as compared to the total width of the sides 24, thus assuring maximum alignment between the button and base. By having at least one guide means on each side of the button, it is possible to have close alignment between the button and the base. By maintaining a small width of groove in relation to rail engagement, the actual bearing surface between these elements is such as to provide minimum tilt of button 22 to base as viewed in FIG. 2.

FIG. 6 illustrates the means for providing a snap-on connection between the button and the base. At the top of each of the grooves 58 is a shoulder forming an ouwardly-extending hook 62. At the bottom of each of the rails 60 there is a shoulder forming an inwardlyextending hook 64. The button, in assembly, is pushed down until the hook 64 snaps over the hook 62, thus securing the button to the base. The button may move up and down on the base, but it cannot be removed from the base unless there is an outward lateral pull on the bottom of the button to release the interlocking hooks.

Of importance is the fact that the button completely masks the base. When the switch is used in a keyboard configuration there is always the possibility of coffee or some other liquid or food being spilled on top of the keyboard. By having the skirt of the button totally mask or shroud the base, there is no possibility of liquid getting into the electrical switching area. In this connection, in the modified form of FIG. 8, the button has an outwardly-extending skirt 66 which bridges the area between adjacent buttons and further masks or shrouds the base member of the switch.

In the modification of FIGS. 9-13, the switch 12 is effectively twice the size of the switch 10. The operating portion of the base 70, as illustrated in FIG. 10, is the same as the base 20 of FIG. 4. However, extending outwardly from opposite sides of the base 70 are mounting portions 72 which provide the guide means. Opposite sides 74 and 76 do not have the guide means which were on each of the sides in the construction of FIGS. l-7. There are grooves 78 in each of the extensions 72 on each side thereof and there are aligned mating rails 80 positioned on the interior of the button 82. Note FIG. 12. In addition to the grooves 78 on the sides of the extensions 72, there are grooves 84 at the ends of each of the extensions 82 and there are mating rails 86 which fit within the grooves 84 as the button is telescopically moved on the base.

As shown in FIG. 11, there are shoulders forming outwardly directed hooks 88 near the top. of each of the grooves 78 and there are inwardly-directed hooks 90 on each of the rails 80. Note that in the snap-on con nection of FIG. 6, the inwardly-directed hooks 64 on the rails are rather sharp in configuration, whereas, the

hooks 90 on the rails are more gentle in slope. Either form of hook is satisfactory. There is no snap-on interconnection between grooves 84 and rails 86.

Of importance in the invention is the fact that the switching elements are formed and arranged to have exceptionally long life. This is brought about by having a contact arm which has an effective length greater than its actual length, with the actual length being greater than any one of the sides of the base. The greater the effective length of the contact arm, the greater the permissible flexing of the arm without excessive fatigue of the contact arm material. Both the contact arm portion and the contact arm itself are cantilever elements. Each are relatively thin and substantially flat, whereby the application of force to the end of the arm portion is distributed generally uniformly throughout the arm portion and the contact arm itself, thus distributing the application force over a substantial length of the metal to provide substantially longer contact life.

The guide means along each of the sides of the button maintain appropriate alignment of the button on the base and prevent the button from being cocked or misaligned. This is a substantial improvement over prior switch constructions in which the guide means were at the center of the base. In order to have a centertype arrangement and yet one which provides precise alignment between the button and the base, it would be necessary to have such a small rail and groove cross section, or a combination having such a small bearing surface that there would be no strength in the rail and hence it would be easily broken. By providing a plurality of guide means and by moving them out to the outside of the switch, the advantages of small bearing surfaces can be utilized in such a manner that there is no loss of strength in the interconnection between the button and the base.

Whereas the preferred form of the invention has been shown and described herein, it should be realized that there may be many modifications, substitutions and alterations thereto.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A pushbutton switch including a base, a button, cooperating means on said button and said base for mounting said button for telescopic movement toward and away from said base, spring means positioned between said button and said base and normally biasing said button away from said base, a pair of terminals extending outwardly from the base, one of said terminals supporting a relatively thin substantially flat flexible cantilever contact arm positioned within the base, said contact arm extending to a position immediately adjacent the other terminal and having an area disposed for contact with said other terminal, said contact arm having a relatively thin substantially flat flexible cantilever portion which extends outwardly from adjacent said area toward the button, means on the button positioned to contact said arm portion and apply force thereto in the direction of button movement and thus move said arm into contact with the other terminal when the but ton is moved relative to the base, said contact arm and arm portion having generally uniform flexibility over their entire path of movement, with said arm area beginning its movement toward said other terminal substantially simultaneously with initial engagement of said button means and said arm portion, the application force of the button being distributed along the cantilever arm portion and the cantilever contact arm, with the combined length of the cantilever arm portion and cantilever contact arm being greater than the distance between said terminals.

2. The structure of claim 1 further characterized in that said base has a plurality of sides, said contact arm extending generally from one corner of the base toward another corner of the base.

3. The structure of claim 2 further characterized in that said base has four sides, with the contact arm extending between opposite corners thereof.

4. The structure of claim 1 further characterized in that said contact arm extending portion is formed integral with the contact arm and is a cut-out portion thereof.

5. The structure of claim 1 further characterized in that said relatively thin substantially flat flexible cantilever contact arm includes a wedge-shaped area positioned immediately adjacent the other terminal and a thin area connecting the wedge-shaped area to the terminal portion, said flexible cantilever portion of said contact arm being integral with said contact arm and a cut-out portion of said wedge-shaped area.

6. The structure of claim 2 further characterized in that the button has the same number of sides as the base and has generally the same configuration, cooperating guide means positioned between at least two of the mating sides of the button and base to align the button as it telescopically moves on the base.

7. The structure of claim 6 further characterized in that said cooperating guide means includes grooves along the sides of the base and mating rails formed along adjacent sides of the button.

8. The structure of claim 7 further characterized in that each of the rails closely fits within its mating groove, with the width of the rail and groove being substantially less than the length of the sides of the base and button including the rail and groove.

9. The structure of claim 6 further characterized by and including means on each of the guide means for forming a snap-on connection between the button and base.

10. The structure of claim 9 further characterized in that each of said cooperating guide means includes a groove on one of the base and button and a rail on the other, with each of the grooves and rails including cooperating hood members for forming the snap-on connection.

l l. The structure of claim 2 further characterized by and including a ledge along the bottom of each side of the base, said ledge being formed and adapted to receive a strain relieving member.

12. The structure of claim 11 further characterized by and including a plurality of downwardly-extending feet on the bottom of the base.

13. The structure of claim 1 further characterized in that said button has an outwardly and downwardly exextends peripherally outside of the base. 

1. A pushbutton switch including a base, a button, cooperating means on said button and said base for mounting said button for telescopic movement toward and away from said base, spring means positioned between said button and said base and normally biasing said button away from said base, a pair of terminals extending outwardly from the base, one of said terminals supporting a relatively thin substantially flat flexible cantilever contact arm positioned within the base, said contact arm extending to a position immediately adjacent the other terminal and having an area disposed for contact with said other terminal, said contact arm having a relatively thin substantially flat flexible cantilever portion which extends outwardly from adjacent said area toward the button, means on the button positioned to contact said arm portion and apply force thereto in the direction of button movement and thus move said arm into contact with the other terminal when the button is moved relative to the base, said contact arm and arm portion having generally uniform flexibility over their entire path of movement, with said arm area beginning its movement toward said other terminal substantially simultaneously with initial engagement of said button means and said arm portion, the application force of the button being distributed along the cantilever arm portion and the cantilever contact arm, with the combined length of the cantilever arm portion and cantilever contact arm being greater than the distance between said terminals.
 2. The structure of claim 1 further characterized in that said base has a plurality of sides, said contact arm extending generally from one corner of the base toward another corner of the base.
 3. The structure of claim 2 further characterized in that said base has four sides, with the contact arm extending between opposite corners thereof.
 4. The structure of claim 1 further characterized in that said contact arm extending portion is formed integral with the contact arm and is a ''''cut-out'''' portion thereof.
 5. The structure of claim 1 further characterized in that said relatively thin substantially flat flexible cantilever contact arm includes a wedge-shaped area positioned immediately adjacent the other terminal and a thin area connecting the wedge-shaped area to the terminal portion, said flexible cantilever portion of said contact arm being integral with said contact Arm and a cut-out portion of said wedge-shaped area.
 6. The structure of claim 2 further characterized in that the button has the same number of sides as the base and has generally the same configuration, cooperating guide means positioned between at least two of the mating sides of the button and base to align the button as it telescopically moves on the base.
 7. The structure of claim 6 further characterized in that said cooperating guide means includes grooves along the sides of the base and mating rails formed along adjacent sides of the button.
 8. The structure of claim 7 further characterized in that each of the rails closely fits within its mating groove, with the width of the rail and groove being substantially less than the length of the sides of the base and button including the rail and groove.
 9. The structure of claim 6 further characterized by and including means on each of the guide means for forming a snap-on connection between the button and base.
 10. The structure of claim 9 further characterized in that each of said cooperating guide means includes a groove on one of the base and button and a rail on the other, with each of the grooves and rails including cooperating hood members for forming the snap-on connection.
 11. The structure of claim 2 further characterized by and including a ledge along the bottom of each side of the base, said ledge being formed and adapted to receive a strain relieving member.
 12. The structure of claim 11 further characterized by and including a plurality of downwardly-extending feet on the bottom of the base.
 13. The structure of claim 1 further characterized in that said button has an outwardly and downwardly extending skirt portion about the periphery thereof which extends peripherally outside of the base. 